Conventionally, a working vehicle including a cab and a working part that are disposed on a slewing base provided on the upper side of a travelling vehicle is used. For example, a crane vehicle includes a slewing base that is turnable with respect to a travelling vehicle, and a cab and a crane part are disposed on the upper side of the slewing base. The crane part can be freely extended and contracted, and is contracted and laid along the travelling vehicle when the crane operation is completed. With this configuration, the travelling vehicle can stably travel.
Here, in general, a crane part is longer than a travelling vehicle, and, when the crane part is laid along the travelling vehicle, the end part of the crane part protrudes from the front part of the travelling vehicle. In view of this, disadvantageously, the end part of the crane part can possibly block the visibility of the operator operating in the cab when the crane vehicle travels on the road. For example, when the crane vehicle enters an intersection and the end part of the crane part is located between the cab and the signal, the operator in the cab cannot clearly check the traffic light in some situation.
In view of this, as a technique of maintaining the clear visibility of the operator in the cab during travel, PTL 1, for example, discloses a slewing excavator in which the cab is supported by a slewing arm such that the cab can be slewed to the rear part of the upper slewing body. When the slewing excavator travels on the road, the slewing excavator slews the cab to the rear side of the upper slewing body, and thus can prevent the working machine from blocking the visibility of the operator in the cab.